Crab shell powder offers novel malaria control method

Scientists have developed a non-toxic mixture of crushed
crab shells and silver nanoparticles that can kill larvae and pupa of
malaria-spreading mosquitoes. The mixture could help halt the spread of
disease-carrying mosquitoes.

Researchers from the National Institute of Communicable
Disease Centre in Coimbatore, India along with colleagues from Taiwan, Saudi
Arabia and Italy used chitosan, a non-toxic biomaterial derived from crab and
lobster shells, to make the mixture. Chitosan has earlier been used in wound
healing, membrane water filters and biodegradable food package coating.

Chitosan-fabricated silver nanoparticles (Ch-AgNP) were
found to be highly toxic to Anopheles
sundaicus, a malaria vector. In laboratory experiments, the mixture showed 100%
larval reduction in 72 hours. The researchers then sprayed the mixture over six
water reservoirs. "Even in small concentrates, it killed mosquito larvae
and pupa quite effectively," they report.

The nanosized particles pass through the insect cuticles
into individual cells and interfere with various physiological processes in the
mosquito's life cycle, the researchers say. The solution did not have any
detrimental effect on goldfish (Carassiu
auratus), which is a natural predator of mosquito larvae "indicating
that it is an environmentally friendly and non-toxic product." The mixture
also inhibited the growth of disease-causing bacterial species such as Bacillus subtilis, Escherichia coli,
Klebsiella pneumoniae and Proteus
vulgaris.

Ch–AgNP may offer a novel and safer control strategy against
A. sundaicus mosquito vectors, as
well as against Gram-negative and Gram-positive pathogenic bacteria. The
finding also suggests that chitosan-based products "could potentially be
less harmful to non-target insects compared to conventional insecticides.